function deepMerge(obj1, obj2) {
  if (!isObj(obj1) || !isObj(obj2)) return shallowMerge(obj1, obj2);

  for (let key in obj2) {
    if (isObj(obj1[key])) {
      obj1[key] = deepMerge(obj1[key], obj2[key]);
    } else {
      obj1[key] = obj2[key];
    }
  }

  return obj1;
}
console.log('深合并--deepMerge', deepMerge(obj4, obj));
